Each golf club within said category of golf clubs will provide superior playing characteristics compared to prior art golf clubs because each golf club of the present invention exhibits lower axial inertia than prior art golf clubs. Where lower axial inertia is defined as lower rotational inertia about the club shaft longitudinal axis. All golf clubs ranging from the driver through high lofted sand wedges are embodied in the present invention. The club heads of the present invention features:
A. Uniquely positioned hosel centerline relative to the club head heel
B. Unique heel-sole-toe weighting configuration
C. Predetermined sequence of golf club head loft angle, club face curvature, lie angle and leading edge progression
D. Unique golf club head appearance
A dictum of golf technique is that the club face should remain parallel to and on the swing plane except near the impact point. To remain within said dictum and to obtain the desired delayed hit, the golfer must rapidly rotate the club shaft 90 degrees about its longitudinal axis just prior to impact. The delayed hit is defined as the condition where the golfer is able to maintain the club face parallel to and on the swing plane until approximately the last 90 degrees of swing arc just prior to impact with his wrists in a fully cocked position and then while releasing from said cocked position rotate the club shaft 90 degrees about its longitudinal axis and then make proper contact with the golf ball. To facilitate this rapid rotation of the club shaft, the present invention will provide lower axial inertia golf clubs when compared to prior art golf clubs. Hereafter, in the discussion of the present invention, the term shaft axis is defined as the club shaft longitudinal axis and the term axial inertia will be defined as the rotational inertia about the club shaft longitudinal axis. Prior art does not address this important issue of providing a low axial inertia golf club to aid the golfer in achieving said desired delayed hit, nor does the prior art discuss any heel-sole-toe weighting configuration constraints on the club head design to achieve a low axial inertia golf club. The present invention lowers the axial inertia by moving the club head center of gravity in closer to the shaft axis centerline. The reduction of the axial inertia is achieved by placing the following configuration constraints on the design of the club heads of the present invention:
1. The hosel centerline, which is an extension of the shaft axis, shall be located away from the extremity of the club head heel and towards the toe end to accomodate the unique heel weighting of the present invention but in no case shall said hosel center line be located further away from the heel extremity than 0.625 inch. Prior art U.S. Pat. No. 3,860,244 refers to said 0.625 inch dimension, but said prior art patent does not address the issue of heel-sole-toe weighting to obtain the unique club head characteristics of the present invention. With the exception of this single dimensional similarity, the differences in the concept of said prior art patent and the present invention are overwhelming.
2. Heel weighting whether it is intrinsic or extrinsic to the club head shall be deposited on the side of the shaft axis opposite to the impact side of said shaft axis. Said heel weighting shall be deposited close to the club head sole to maintain a low club head center of gravity. Prior art does not address the fact that the heel weighting should be located on the side of the shaft axis opposite to the impact side in order to lower the club head axial inertia. Nor does prior art discuss the advantage of having heel weighting deposited close to the sole in order to obtain a low club head center of gravity.
3. Sole weighting on the wood club heads whether it is intrinsic or extrinsic to the club head shall be deposited towards the impact plane to obtain a club head center of gravity location which is closer to the impact plane than prior art wood club heads. "The impact plane is defined as a vertical plane that intersects the golf ball impact point on the club face and is perpendicular to the horizontal component of the golf ball launch direction." A center of gravity location which is closer to the impact plane will reduce the gear effect side spin caused by off-line swing path impacts. Prior art does not address the importance of having the club head center of gravity close to the impact plane in regards to reducing the gear effect side spin. Gear effect side spin is well discussed in U.S. Pat. No. 4,471,961.
4. Toe weighting whether it be intrinsic or extrinsic to the club head shall be used to reduce the adverse effects of off-center impacts but not to an extent that the basic intent of the invention is compromised, where said basic intent is to lower the club head axial inertia. Said toe weighting shall be deposited close to the impact plane to minimize gear effect side spin caused by off-line swing path impacts, and deposited close to the club head sole to maintain a low club head center of gravity. A low center of gravity will tend to yield a low axial inertia club head. Prior art does not discuss the important relationship between low center of gravity and low axial inertia club heads.
5. The crown apex of wood club heads shall be further forward towards the club face when compared to prior art wood club heads, and whereby the crown tapers off rapidly from its apex towards the rear of the club head to obtain a low profile club head which tends to lower the club head center of gravity. Prior art does not discuss this method of crown apex placement to obtain a low club head center of gravity.
The object of this invention is to:
1. Provide a golf club head design which improves the playing characteristics of both woods and irons by reducing the axial inertia of said golf club head. Low axial inertia club heads will be produced by reducing the distance between the center of gravity to the shaft axis centerline. Prior art does not address the importance of low axial inertia club heads in regards to the achievement of the delayed hit.
2. Provide a low club head center of gravity. This low center of gravity will aid the present invention's goal of obtaining low axial inertia club heads. Prior art does not discuss the relationship between club head low center of gravity and low axial inertia.
3. Provide one configuration of golf clubs whereby the iron club heads and the offset hosel wood club heads will have a hosel centerline which intersects a horizontal line which is on the impact plane and where said horizontal line intersects the expected impact point. This predetermined relationship of the hosel to the club head will provide the golfer with a consistent feel for precisely when the club head will make contact with the ball relative to the position of the shaft axis. Prior art does not specifically discuss said predetermined relationship and its subsequent advantage.
4. Provide a wood golf club head wherein all the heel-sole-toe weighting material is deposited as close to the impact plane as practical. With said heel-sole-toe weighting material up near the impact plane, a reduction of gear effect side spin on off-line swing path impacts will be realized when using a wood golf club of the present invention. Prior art does not discuss the issue of providing a club head center of gravity close as practical to the impact plane in order to minimizes the gear effect side spin.